1. Field of the Invention
This invention relates to the field of very heavy doors allowing in particular access to a closed space in a hostile environment and more particularly a closed space in a nuclear power plant, and it has as its object an oscillating-mount split-hinge device that is designed to be fitted on such very heavy doors. It also has as its object such a very heavy door that is equipped with said split-hinge device.
2. Description of the Related Art
It is known that a conventional door split-hinge that comprises a flap that pivots around a vertical axis consists of, on the one hand, two split-hinge parts—one of which, stationary, is mounted on the frame, and the other, movable, is mounted on said pivoting flap—and, on the other hand, a pivoting shaft—generally integral with the frame or, if necessary, the flap, which makes it possible to guide the unit in rotation by sliding, around said pivoting shaft, one of said split-hinge parts relative to the other.
The existing split-hinges are fitted on all types of doors of different weights, but those that are fitted on very heavy doors, weighing several tons, are to support axially significant loads, whose requirements and the actual standards in terms of safety are very high.
This is particularly the case of very heavy doors that are installed, using cranes, in hostile environments such as nuclear power plants and in particular in the building of said power plants that contains the nuclear reactor.
Split-hinge systems that are fitted on such very heavy doors that generally comprise a lower split-hinge that is designed to support at least the bulk of the load of the flap of the door and an upper split-hinge that is designed primarily to form an anti-tilting holding point and axial guide of the flap of said door are already known.
In a split-hinge system of this type, the lower split-hinge and the upper split-hinge each comprise a respectively lower and an upper pivoting shaft, making it possible to guide in rotation the respectively lower and upper movable split-hinge part relative to the respectively lower and upper stationary split-hinge part around said pivoting shaft, and this is done by insertion of roller bearing means.
Furthermore, the pivoting of the flap of the door for its opening or closing is done by a mechanical crank system or by a power unit, whose motor is generally attached to the frame and drives a rotary shaft that is integral with the flap and in particular the movable split-hinge part of the lower split-hinge.
It has been noted, however, that when such a very heavy door is opened, bending frequently occurs at the frame, producing an offsetting movement of the two respectively upper and lower split-hinges, which generates considerable friction at one and/or the other of the axes of said split-hinges, which has the effect of causing jamming between the axis in question and the corresponding split-hinge, and an increased pivoting force during the closing or opening movements of the pivoting flap of said door.
However, if the opening or the closing of the flaps of such very heavy doors can nevertheless be performed, even in the offset state, owing to the use of high-power power units to counteract the friction generated by said state, this goes against current economic requirements in terms of reducing production costs of such doors and lowering the consumption of said power units, which can be accomplished only by the use of power units of limited power.
The document FR 829 875 has as its object a joint device for the panel of a door by means of a pivot upright that consists of a metal pipe that is engaged at its lower end on a pivot that forms a step bearing that is sealed in the ground and at its upper end on a pivot, whereby said ends are locked respectively by an upper head and a lower head, while a spherical ball is inserted between the bottom of the lower head and the upper surface of the lower pivot.
However, this type of device that comprises a metal pipe, forming a hinge, requiring a sealing of its lower end in the ground by means of a step bearing by means of in particular a spherical ball, does not allow a sufficiently effective operation of the joint for an application to a very heavy door, in particular a door that is used in a nuclear power unit. In addition, the very heavy doors that are used in the nuclear field should be able to resist or withstand an earthquake, which does not allow a joint device such as the one that is described in the above-mentioned document, fitted on such a door. Actually, in this type of device, during an earthquake that produces combined movements of the door in several directions, the ball leaves its housing, thereby affecting the behavior and the resistance of the door during these sudden movements.